Can I change the default working directory in quarto.qmd to ../ in just one line? There are so many of the image and I don't want to change them one by one everytime.
Changing  to  somehow doesn't seem to work in a Quarto project. It seems to parse the path to root/.../image.png.
Quarto project are meant to be the wider scope to use, meaning you can't really access some resources outside of the project, especially relatively (using ../quarto project).
So you won't be able to access images outside of the project. Basically, the answer is you can't change what a Quarto project means.